// Gets if the type can be constructed from the given list of expressions
public static bool CanConstructType(ShaderType type, List <ExprResult> args, out string error)
{
error = null;
if (type == ShaderType.Void)
{
error = "Cannot construct the 'void' type.";
return(false);
}
if (type.IsHandleType())
{
error = $"Cannot manually construct a handle type ('{type}').";
return(false);
}
// Immediately fail if any arguments are arrays or handle types
var badarg = args.FindIndex(arg => arg.IsArray || arg.Type.IsHandleType());
if (badarg != -1)
{
error = $"Type construction argument {badarg} cannot be an array or handle type ({args[badarg].Type}[{args[badarg].IsArray}].";
return(false);
}
if (!type.IsMatrixType()) // Vectors and scalars
{
var ccount = type.GetComponentCount();
if (ccount == 1) // Scalars
{
if (args.Count != 1)
{
error = "Scalar constructors can only have one argument.";
return(false);
}
if (!args[0].Type.IsScalarType())
{
error = "Scalars can only be constructed from other non-array scalar types.";
return(false);
}
return(true);
}
else // Vectors
{
var comptype = type.GetComponentType();
if (args.Count > ccount) // Too many arguments
{
error = $"Too many arguments for constructing vector type '{type}'.";
return(false);
}
if (args.Count == 1) // Direct casting between vectors -or- filling out entire vector with one value
{
if (args[0].Type.IsScalarType())
{
if (!args[0].Type.CanPromoteTo(comptype))
{
error = $"Cannot construct vector type '{type}' from scalar type '{args[0].Type}'.";
return(false);
}
return(true);
}
if (!args[0].Type.IsVectorType() || (args[0].Type.GetComponentCount() < ccount))
{
error = "Can only cast between vector types of the same size or larger (through concatenation).";
return(false);
}
if (!args[0].Type.CanPromoteTo(type))
{
error = $"No casting rules exist to cast a '{args[0].Type}' vector to a '{type}' vector.";
return(false);
}
return(true);
}
if (args.Count == ccount) // Directly supplying each component
{
var bidx = args.FindIndex(arg => !arg.Type.IsScalarType() || !arg.Type.CanPromoteTo(comptype));
if (bidx != -1)
{
error = $"Type constructor argument {bidx} must be a '{comptype}' compatible non-array scalar type.";
return(false);
}
return(true);
}
else // Some mix of other argument types
{
var bidx = args.FindIndex(arg => arg.Type.IsMatrixType() || !arg.Type.GetComponentType().CanPromoteTo(comptype));
if (bidx != -1)
{
error = $"The type constructor argument {bidx} must be a '{comptype}' compatible non-array scalar or vector type.";
return(false);
}
var csum = args.Sum(arg => arg.Type.GetComponentCount());
if (csum != ccount)
{
error = $"The type constructor arguments must provide the exact numer of components required ({ccount} != {csum}).";
return(false);
}
return(true);
}
}
}
else // Matrices
{
if (args.Count == 1) // Constructing a diagonal matrix, or a direct matrix cast
{
if (args[0].Type.IsMatrixType())
{
return(true); // Direct matrix casts always work
}
if (!args[0].Type.IsScalarType() || !args[0].Type.CanPromoteTo(ShaderType.Float))
{
error = $"Diagonal matrices can only be constructed from capatible scalar types.";
return(false);
}
return(true);
}
// Simply need enough compatible arguments to fill each matrix component exactly
var bidx = args.FindIndex(arg => arg.Type.IsMatrixType() || !arg.Type.GetComponentType().CanPromoteTo(ShaderType.Float));
if (bidx != -1)
{
error = $"The matrix constructor argument {bidx} must be a 'Float' compatible scalar or vector type.";
return(false);
}
var csum = args.Sum(arg => arg.Type.GetComponentCount());
var tsum = (type == ShaderType.Mat2) ? 4 : (type == ShaderType.Mat3) ? 9 : 16;
if (tsum != csum)
{
error = $"Matrix constructors must be given exactly enough arguments to fill their components ({csum} != {tsum}).";
return(false);
}
return(true);
}
}
